1. Field of the Invention
The present invention relates to a head suspension assembly, such as those used in magnetic disk units, particularly to a head suspension assembly wherein a tube, through which pass a plurality of covered wires, is clamped, and a manufacturing method thereof.
2. Description of the Related Art
In a head suspension assembly used in magnetic disk units as shown in FIG. 2(a), a tube 5 (having a plurality of covered wires 4 passing therethrough which connect with a head slider 1) is fixed and clamped by claw section 6. Claw section 6, on the side of a mount plate 3, is connected with a head actuator (not illustrated). FIG. 2(b) is an enlarged drawing thereof. The tube 5 is fixed by clamping such a claw section 6, thereby fixing the covered wires inserted into the tube 5 so that they do not move. This is done for the following reasons. That is, as shown in FIG. 3(a), there is normally a fairly large space between the tube 5 and the covered wires 4 because the covered wires 4 are thinner compared to the inside diameter of the tube 5. Therefore, as shown in FIG. 3(b), the friction force between the tube 5 and the covered wires 4 is not increased unless the tube 5 is clamped sufficiently, with the result that the covered wires 4 move easily when pulled.
There is another method for fixing the covered wires 4 so that they are not easily moved when pulled. As shown in FIGS. 4(a) and 4(b), in some cases adhesive is applied to the covered wires 4 and hardened in a ball shape 9 on the side where the head slider 1 in the head suspension assembly is connected, so that ball 9 of this adhesive is caught at the head of the tube 5 even if the covered wires 4 are pulled from the mount plate side, thereby preventing the covered wires 4 from moving.
Moreover, although it is not a head suspension assembly in which the covered wires are fixed by clamping the tube to prevent the covered wires in the tube from moving, in Japanese PEPA No. 2-40205, a fixture section 14 is formed on a lead wire 13 which is inserted into a through hole 12 of a cylindrical ferrite bead 11, a liquid adhesive 15 is applied to the fixture section 14 (see FIG. 5). The fixture section 14 is inserted in the through hole 12 so as to form a capillary gap 16 between the through hole 12 and the lead wire 13 (see FIG. 6), and then, the adhesive 15 is heated to a lower viscosity, and the adhesive 15 is infiltrated into the through hole 12 from outside by capillary action using the capillary gap 16 so as to fill in the through hole 12 (see FIG. 7).
An element assembly of electronic parts such as this ferrite bead might be broken if clamped. Thus, in such a technique as disclosed in Japanese PEPA No. 2-40205, it is not possible to fix lead wires by clamping so that lead wires in a through hole do not move. Therefore, this method is not suitable for practical use where clamping is utilized.
In a conventional method where a tube is clamped to fix covered wires therein so that they do not move, if a claw section is clamped too strongly, then a crack is produced on the tube or the covered wires may be cut or short-circuited. Such a crack or short-circuit renders the manufactured head suspension assembly unusable.
On the other hand, if the claw section is insufficiently clamped, this may avoid such problems, but the covered wires in the tube are not fixed securely and move easily. Therefore, the covered wires will move easily when they are pulled at the time of soldering, resulting in deformation of the head suspension assembly. If deformations arise in this loop shape, then the flying height, which is the most important parameter of the head suspension assembly, will be changed. Therefore, the yield of the products using a head suspension assembly such as a magnetic disk unit will decrease.
Moreover, the method of forming a ball of adhesive at the head of covered wires on the slider side has a disadvantage in that the position and size of the ball of adhesive must be accurately controlled. This is because unevenness has a bad influence directly onto the loop shape of the covered wires. As a result, the flying height will be changed and problems arise, such as the decreased yield of products using a head suspension assembly (e.g., magnetic disk units).
As stated above, in a head suspension assembly, it is not possible by conventional methods to fix the covered wires inserted into a tube so that they do not move, or even if it were possible to carry out, problems arose, and these methods were not suitable for practical use.